The invention relates to methods and compositions for preserving blood samples. In particular, a method for stabilizing glucose level in a blood sample is provided, which method comprises adding an effective amount of glyceraldehyde to a blood sample, whereby glucose level in said blood sample remains substantially constant for a period of time. Kits and combinations for stabilizing glucose level in a blood sample are also provided.
Glucose is one of the most commonly measured components of blood, because of the central role of glucose in metabolism and the high prevalence of diseases of glucose homeostasis. A continuing problem in the accurate measurement of glucose is the loss of glucose from specimens due to glycolysis by erythrocytes during transport and processing (Sidebottom et al., Clin. Chem., 28:190-2 (1982)). In recent years, this phenomenon has been more evident, as laboratory services have consolidated and many more specimens are transported to distant laboratories for analysis. Several approaches have been proposed to minimize glycolysis, including centrifugation/decantation of plasma immediately after specimen collection (Sidebottom et al., Clin. Chem., 28:190-2 (1982), refrigeration/cooling on ice during transport (Lin et al., Clin. Chem., 22:2031-3 (1976)), addition of anti-glycolytic agents such as iodoacetate (Bueding and Goldfarb, J. Biol. Chem., 141:539-44 (1942)), fluoride (Denis and Beven, J. Lab. Clin. Med., 9:674-9 (1924)) or mannose (Nakashima et al., Clin. Chem., 33:708-10 (1987)) to the collection tubes, and the use of glucose analyzers designed for near-patient testing, at the bedside (Innanen et al., J. Pediatr., 130:151-5 (1997)). All of these approaches are in current use, and the use of fluoride in blood collection tubes is prevalent in circumstances where substantial delay between collection and analysis is anticipated, but all have significant limitations (for review, see Dietzler and Smith, Carbohydrates. In: Sonnenwirth A C, Jarett L, eds. Gradwohl""s Clinical Laboratory Methods and Diagnosis. Vol I, 8th ed. St. Louis, Toronto, London: CV Mosby Co., 1980:210-49). To various degrees, these approaches are limited in efficacy by either incomplete inhibition of glycolysis, interference in testing for co-analytes (electrolytes, creatinine, urea, etc.), disturbance of cellular integrity such as hemolysis or promotion of leakage of intracellular potassium.
The ideal approach for eliminating glycolytic loss would provide reasonably stable glucose levels for a period needed for transport to a centralized laboratory, avoid costly near-patient centrifugation/special handling/analysis, and yield a specimen that is suitable for analysis of many other common analytes so that separate collection of specimen for those analytes is not necessary. From a practical standpoint, the best way to achieve this goal is discovery of an antiglycolytic agent that can be added to collection tubes but does not alter cellular integrity or interfere in common analytical methodologies. Such an agent should also be effective at low concentration (minimizing volume addition to avoid dilution errors), dissolve rapidly during the collection process, be non-toxic, be stable in the room-temperature storage environment of blood collection devices, and be inexpensive. Glyceraldehyde has these properties as an additive in blood collection devices.
The invention provides methods and compositions for stabilizing glucose level in a blood sample using glyceraldehyde. Kits and combinations for stabilizing glucose level in a blood sample containing glyceraldehyde are also provided.
In one aspect, the invention is directed to a method for stabilizing glucose level in a blood sample, which method comprises adding an effective amount of glyceraldehyde to a blood sample, whereby glucose level in said blood sample remains substantially constant for a period of time.
D-glyceraldehyde, 1-glyceraldehyde, or racemic mixture of d,1-glyceraldehyde can be used. Preferably, 1-glyceraldehyde is used.
Suitable amounts of glyceraldehyde should be used in the methods. If racemic mixture of d,1-glyceraldehyde is used, the final concentration of the racemic mixture of d,1-glyceraldehyde in the blood sample is preferably from about 0.9 to about 20 mM. More preferably, the final concentration of the racemic mixture of d,1-glyceraldehyde in the blood sample is from about 5 to about 10 mM. If 1-glyceraldehyde is used, the final concentration of the 1-glyceraldehyde in the blood sample is preferably from about 0.65 to about 10 mM. More preferably, the final concentration of the 1-glyceraldehyde in the blood sample is from about 2.5 to about 5 mM.
The present method can be used for stabilizing glucose level in any blood sample. Preferably, the blood sample is a whole blood, plasma or serum sample. More preferably, the whole blood sample is a heparinized whole blood sample.
The present method can be used for stabilizing glucose level in a blood sample with any concentration of glucose. Preferably, the starting glucose concentration in the blood sample is from about 0 to about 100 mM. More preferably, the starting glucose concentration in the blood sample is from about 3.9 mM to about 13.4 mM.
The present method can be used for stabilizing glucose level in a blood sample so that the glucose level in said blood sample remains substantially constant for a period of time. Sufficient amount of glyceraldehyde can be used so that the starting glucose concentration does not decrease by more than 5%, and preferably, 2%. Similarly, sufficient amount of glyceraldehyde can be used so that the glucose level in the blood sample remains substantially constant for at least about 16 hours, and preferably for at least about 8 hours.
The blood sample that is treated with the present method, i.e., with added glyceraldehyde, can be subjected to a xe2x80x9cmetabolismxe2x80x9d assay. Such metabolism assay can be used in assaying molecules important in metabolism such as inorganic molecules, e.g., O2 or CO2 or inorganic ions such as sodium, potassium, magnesium, calcium, chloride, iron, copper, zinc, manganese, cobalt, iodide, molybdenum, vanadium, nickel, chromium, fluoride, silicon, tin, boron or arsenic ions. Such metabolism assay can also be used in assaying organic molecules including amino acids, peptides, nucleosides, nucleotides, oligonucleotides, vitamins, monosaccharides, oligosaccharides or lipids. Class of molecules, e.g., proteins, nucleic acids, lipids or carbohydrates can also be assayed.
Preferably, the metabolism assay is used in assaying ions such as sodium, potassium, chloride and calcium ions, glucose, creatinine, urea, bilirubin, albumin, alkaline phosphatase activity, aspartate aminotransferase (AST), total protein and total CO2. Also preferably, the metabolism assay is operated on an automated analyzer such as Ortho-Clinical Diagnostics Vitros 250, Dade Behring RxL and Hitachi 747 analyzer.
In another aspect, a kit for stabilizing glucose level in a blood sample is provided, which kit comprises: a) an effective amount of glyceraldehyde; and b) an instruction indicating that said kit is used for stabilizing glucose level in a blood sample.
In still another aspect, a combination for stabilizing glucose level in a blood sample is provided, which combination comprises: a) an effective amount of glyceraldehyde; and b) an effective amount of an anti-glycolytic agent that is not glyceraldehyde. This combination is useful in a method for stabilizing glucose level in a blood sample, which method comprises adding an effective amount of glyceraldehyde and an effective amount of an anti-glycolytic agent that is not glyceraldehyde to a blood sample, whereby glucose level in said blood sample remains substantially constant for a period of time. In this method, the glyceraldehyde and the anti-glycolytic agent can be added to the blood sample simultaneously or sequentially.
In yet another aspect, a combination for preserving a blood sample for a further analysis is provided, which combination comprises: a) an effective amount of glyceraldehyde; and b) an effective amount of a blood-preserving agent. This combination is useful in a method for preserving a blood sample for a further analysis, which method comprises adding an effective amount of glyceraldehyde and an effective amount of a blood-preserving agent to a blood sample, whereby the quality of said blood sample is substantially preserved for a further analysis. In this method, the glyceraldehyde and the blood-preserving agent can be added to the blood sample simultaneously or sequentially.